Administration sets for intravenously administering a liquid, generally called a transfusion liquid, and sometimes containing a dextrose solution, a solution of salt or water (hereafter called a medical liquid), are widely used. In such a set a particular drug is frequently mixed with the medical liquid to be administered.
The administration set generally comprises a container containing a large volume of medical liquid, a cylindrical instillator, and flow rate control means, a fluid filter, means for removing air, an injection site for injecting additional drug mixture, fluid conduits for connection, and means for coupling inlet and outlet portions.
Conventionally, when the administration set is used to supply a patient with a medical liquid mixed with a particular agent, if the agent is not liquid, it is first liquefied by using a diluent or other agent and then infused into the injection site so that the agent is mixed with the medical liquid.
This method, however, carries a risk of various kinds of contamination that are attributable to the requirements for the work of infusing a drug into the medical solution and preparatory operations therefor.
Various countermeasures have been taken to avoid these risks, and to relieve medical workers from the work.
Representatives of such countermeasures are described in Japanese Patent Publication Nos. 5-60758 and 5-81271. The systems taught by these publications comprises disposing a vial-like drug container in the middle of a fluid conduit for a medical liquid, and passing the medical liquid through the drug container to deliver a mixed solution containing the medical solution and drug. This type of system is referred to as a "passive drug delivery system."
In that system a socket or a receptacle and a cartridge to be coupled therewith are provided. The drug container is attached to the cartridge so that, when the cartridge is connected to the receptacle, the inside space of the drug container is made to communicate with the flow path of the medical solution.
In this passive drug delivery system, once the drug container is docked in the cartridge, there is no chance for the drug in the container to be exposed to the air, and the mixing operation is automatically carried cut by the medical solution, so that a very high degree of safety can be secured, and so that the operator's labor can be avoided.
However, in the conventional system it is generally assumed that once the vial has been docked to start the administration, all the administration components should be maintained as they are. Thus, requirements such as enabling rapid administration while keeping the drip speed constant, automatically completing the administration of the entire agent without fear of contamination, and adaptively and smoothly removing or exchanging the used vial, are not necessarily adequately considered.
Therefore the purpose of this invention is to provide an improved passive drug delivery apparatus of a simple structure enjoying the advantages of the passive drug delivery system, wherein normal drug delivery can be rapidly started when necessary, and wherein the interruption of drug delivery, the exchange of a vial, and the complete delivery of the entire drug, can easily be carried out.